U.S. patent number 8,116,875 [Application Number 11/818,728] was granted by the patent office on 2012-02-14 for implantable neurostimulation systems.
This patent grant is currently assigned to Neuropoint Medical, Inc.. Invention is credited to Hyoung-Ihl Kim, Thomas P. Osypka, Yong-Il Shin.
United States Patent |
8,116,875 |
Osypka , et al. |
February 14, 2012 |
Implantable neurostimulation systems
Abstract
New and useful neurostimulation systems are provided that
include an implantable pulse generator dimensioned and configured
for implantation in the skull of a patient. The implantable pulse
generator has an electrode operatively associated with a distal end
portion thereof and can be provided with adjustment means, such as
an adjustable biasing member or spring arranged between the
electrode to the distal end portion of the pulse generator. Also
provided are systems involving networked neurostimulators that are
configured and adapted to work jointly in accordance with
prescribed treatment protocol to effect a desired recovery from
brain injury. Such networked neurostimulation systems are
particularly advantageous for effecting relatively large and/or
relatively distant regions of the brain. Additionally, systems and
methods for motor-evoked potential (MEP)-based neuromodulation are
provided. Further, AC and/or DC stimulation can be utilized,
depending on the precise implementation.
Inventors: |
Osypka; Thomas P. (Palm Harbor,
FL), Kim; Hyoung-Ihl (Jeonbug, KR), Shin;
Yong-Il (Iksan, KR) |
Assignee: |
Neuropoint Medical, Inc. (Palm
Harbor, FL)
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Family
ID: |
38877674 |
Appl.
No.: |
11/818,728 |
Filed: |
June 15, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080004676 A1 |
Jan 3, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60814617 |
Jun 16, 2006 |
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Current U.S.
Class: |
607/45;
607/139 |
Current CPC
Class: |
A61N
1/0539 (20130101); A61N 1/0531 (20130101) |
Current International
Class: |
A61N
1/05 (20060101) |
Field of
Search: |
;607/45,48,139 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2004/050175 |
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Jun 2004 |
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WO |
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WO 2005/011805 |
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Feb 2005 |
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WO |
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WO 2006/019766 |
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Feb 2006 |
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WO |
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Primary Examiner: Layno; Carl H
Assistant Examiner: Behringer; Luther
Attorney, Agent or Firm: Wofsy; Scott D. Edwards Wildman
Palmer LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority under 35 U.S.C. .sctn.119 to U.S.
Provisional Patent Application Ser. No. 60/814,617, filed Jun. 16,
2006, which is hereby incorporated by reference in its entirety.
Claims
We claim:
1. An implantable neurostimulator comprising: a housing; mounting
means for securing the housing and the neurostimulator to a cranium
of a patient; stimulus generating means provided within the housing
for generating a therapeutic electrical stimulus; an electrode for
contacting a dura of a brain of the patient; biasing means arranged
between the mounting means and the electrode for biasing the
electrode toward the brain of the patient and moving the electrode
independent of the housing; a wire electrically connecting the
pulse generating means and the electrode wherein the pulse
generating means is housed in the housing mounted to the patient's
cranium and the electrode is biased against the patient's brain via
the biasing means, the wire adapted and configured to deliver the
electrical stimulus generated by the pulse generating means to the
electrode; and a stem element extending integrally from the housing
and arranged between the housing and the electrode, a length of the
stem setting a minimum distance between the housing and the
electrode.
2. The implantable neurostimulator of claim 1, further comprising
an antenna operatively connected to the pulse generating means, the
pulse generating means receiving a control signal from an external
control unit through the antenna.
3. The implantable neurostimulator of claim 1, wherein the biasing
means is arranged between the housing and the electrode.
4. The implantable neurostimulator of claim 1, wherein the biasing
means is a resilient element.
5. The implantable neurostimulator of claim 4, wherein the biasing
means is a spring.
6. The implantable neurostimulator of claim 4, wherein the biasing
means functions as the electrically conductive element by having at
least an electrically conductive portion.
7. The implantable neurostimulator of claim 1, wherein the biasing
means is one or more shims.
8. The implantable neurostimulator of claim 1, wherein the mounting
means is integrally formed with the housing.
9. The implantable neurostimulator of claim 8, wherein the mounting
means includes one or more extension portions extending from the
housing, adapted and configured to be secured to the cranium of the
patient by one or more mechanical fasteners.
10. The implantable neurostimulator of claim 1, wherein the
mounting means is integrally formed with the stem element, the stem
element directly engaging the cranium of the patient.
11. The implantable neurostimulator of claim 10, wherein the
mounting means includes threads arranged on an outer surface of the
stem element for engaging the cranium of the patient.
12. The implantable neurostimulator of claim 10, wherein the
mounting means includes a textured surface arranged on an outer
surface of the stem element for engaging the cranium of the
patient.
13. The implantable neurostimulator of claim 12, wherein the
textured surface is adapted and configured to promote bone ingrowth
into the neurostimulator, to aid fastening of the neurostimulator
to the cranium.
14. The implantable neurostimulator of claim 1, wherein the
mounting means includes a fastening strap adapted and configured to
engage the housing and to be secured to the cranium of the patient
by one or more mechanical fasteners.
15. The implantable neurostimulator of claim 1, wherein the
mounting means includes a platform element configured and adapted
to be secured to the cranium of the patient by one or more
mechanical fasteners, to which the stem element is also mutually
engageable.
16. The implantable neurostimulator of claim 1, wherein the stem
element functions as the electrically conductive element by having
at least an electrically conductive portion.
17. The implantable neurostimulator of claim 1, wherein the housing
includes a cap portion and a base portion sealed together, forming
the housing.
18. The implantable neurostimulator of claim 1, further comprising
a retainer lip arranged on a lower surface of the housing, adapted
and configured to engage the stem element.
19. The implantable neurostimulator of claim 18, wherein the
retainer lip includes an anti-rotation feature to inhibit relative
rotation between the retainer lip and the stem element.
20. The implantable neurostimulator of claim 1, wherein the housing
is adapted and configured to function as a second electrode, to
complete an electrical circuit with the first electrode when
delivering a therapeutic electrical stimulus.
21. The implantable neurostimulator of claim 1, wherein the housing
is provided with a separate second electrode, carried thereon, to
complete an electrical circuit with the first electrode when
delivering a therapeutic electrical stimulus.
22. The implantable neurostimulator of claim 1, wherein the first
electrode is adapted and configured to slideably engage the stem
element, a biasing element being provided between the electrode and
stem element for urging the first electrode toward the brain of the
patient.
23. The implantable neurostimulator of claim 22, wherein the stem
element is provided with a groove for engaging the biasing element,
to prevent unintentional relative translation between the stem
element and the biasing element.
24. The implantable neurostimulator of claim 1, further comprising
an aperture defined in the housing, configured and adapted to
receive passage of an antenna, extending from the stimulus
generating means outside of the housing.
25. The implantable neurostimulator of claim 24, wherein a
feedthrough element is provided within the aperture to seal an
internal environment of the housing from the external environment
of the housing.
26. The implantable neurostimulator of claim 1, further comprising
an aperture defined in the housing, configured and adapted to
receive passage of a conductor, extending from the stimulus
generating means to the first electrode.
27. A system for therapeutic neurostimulation, the system
comprising: a) a plurality of implantable neurostimulators in
accordance with claim 1; and b) communication means connecting the
plurality of neurostimulators.
28. The system for therapeutic neurostimulation of claim 27,
wherein the plurality of implantable neurostimulators are arranged
in an array in the cranium of the patient.
29. The system for therapeutic neurostimulation of claim 28,
wherein the array is a rectangular array.
30. The system for therapeutic neurostimulation of claim 27,
wherein the array is a circular array.
31. The system for therapeutic neurostimulation of claim 27,
wherein the plurality of implantable neurostimulators are adapted
and configured to communicate with one another by way of a
conductive element provided between implantable
neurostimulators.
32. The system for therapeutic neurostimulation of claim 7, wherein
the plurality of implantable neurostimulators are adapted and
configured to communicate with one another by way of a wireless
signal.
33. The system for therapeutic neurostimulation of claim 27,
wherein at least one implantable neurostimulator is adapted and
configured to receive power from at least one other implantable
neurostimulator by way of a conductive element provided between
implantable neurostimulators.
34. The system for therapeutic neurostimulation of claim 27,
further comprising a programmer provided external to the patient
for programming a predetermined treatment protocol into at least
one of the implantable neurostimulators.
35. The implantable neurostimulator of claim 1 further including a
programming unit remotely located and coupled to the stimulus
generating means operative to control the stimulus generating means
and provide an inductive charge to the stimulus generating means.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention is directed to an implantable stimulation
system, and more particularly, to a new and useful implantable
neurostimulator for stimulating the cerebral cortex of the brain.
The subject invention is also directed to such stimulations systems
that include networked neurostimulators.
2. Description of Related Art
The cerebral cortex is the outer layer of gray matter in the
cerebrum. It consists mainly of neuronal cell bodies and dendrites,
and is associated with higher functions, including language and
abstract thought. The cerebral cortex is 2-4 mm (0.08-0.16 inches)
thick and is folded. The dura mater is the dense fibrous tissue
covering of the brain. It extends between the cerebral hemisphere
as the falx cerebri.
Current neurostimulation systems for stimulating the cerebral
cortex of the brain include a conductive lead having an electrode
at one end for implantation adjacent the dura mater and a connector
at the other end for engaging the header of a pulse generator. The
pulse generator is typically implanted at location remote from the
stimulation site. Additionally, current neurostimulation systems
include neurostimulators that are not capable of working in unison
to effect large and/or distant parts of the brain, and which are
only capable of using AC (alternating-current) stimulation.
SUMMARY OF THE INVENTION
The subject invention is directed to new and useful
neurostimulation systems that include an implantable pulse
generator dimensioned and configured for implantation in the skull
of a patient. The implantable pulse generator has an electrode
operatively associated with a distal end portion thereof and can be
provided with adjustment means, such as an adjustable biasing
member or spring arranged between the electrode to the distal end
portion of the pulse generator. The proximal end portion of the
pulse generator is disposed beneath the scalp and can be adapted
and configured to serve as a receiver for communicating with an
external programming device designed to control the operation of
the pulse generator.
The subject invention is also directed to systems involving
networked neurostimulators that are configured and adapted to work
jointly in accordance with prescribed treatment protocol to effect
a desired recovery from brain injury. Such networked
neurostimulation systems are particularly advantageous for
effecting relatively large and/or relatively distant regions of the
brain that are functionally related.
In accordance with the invention, an implantable neurostimulator is
provided having a housing, mounting means for securing the housing
and the neurostimulator to a cranium of a patient and a stimulus
generating means provided within the housing for generating a
therapeutic electrical stimulus. The neurostimulator further
includes a first electrode for contacting a dura of a brain of the
patient, an electrically conductive element operatively connecting
the pulse generating means and the electrode, adapted and
configured to deliver the electrical stimulus generated by the
pulse generating means to the electrode, and a stem element
arranged between the housing and the electrode, a length of the
stem setting a minimum distance between the housing and the
electrode.
The implantable neurostimulator can further include an antenna
operatively connected to the pulse generating means, the pulse
generating means receiving a control signal from an external
control unit through the antenna.
Additionally, biasing means can be arranged between the mounting
means and the electrode for biasing the electrode toward the brain
of the patient. The biasing means can be arranged between the
housing and the electrode. The biasing means can be a resilient
element, such as a spring. Further, the biasing means can function
as an electrically conductive element by having at least an
electrically conductive portion. Alternatively or additionally, the
biasing means can be one or more shims.
The mounting means can be integrally formed with the housing, and
can include one or more extension portions extending from the
housing, adapted and configured to be secured to the cranium of the
patient by one or more mechanical fasteners. Further, the mounting
means can be integrally formed with the stem element, the stem
element directly engaging the cranium of the patient. The mounting
means can include threads arranged on an outer surface of the stem
element for engaging the cranium of the patient. Alternatively, the
mounting means can include a textured surface arranged on an outer
surface of the stem element for engaging the cranium of the
patient. Such textured surface can be adapted and configured to
promote bone ingrowth into the neurostimulator, to aid fastening of
the neurostimulator to the cranium.
Additionally or alternatively, the mounting means can include a
fastening strap configured and adapted to engage the housing and to
be secured to the cranium of the patient by one or more mechanical
fasteners. Further, the mounting means can include a platform
element configured and adapted to be secured to the cranium of the
patient by one or more mechanical fasteners, to which the stem
element is also mutually engageable. Additionally, the housing can
be adapted to engage the platform element.
In accordance with the invention, the stem element can function as
the electrically conductive element by having at least an
electrically conductive portion.
The housing can include a cap portion and a base portion sealed
together, forming the housing. The neurostimulator can further
include a retainer lip arranged on a lower surface of the housing,
adapted and configured to engage the stem element. The retainer lip
can include an anti-rotation feature to inhibit relative rotation
between the retainer lip and the stem element. Further, the housing
can be adapted and configured to function as a second electrode, to
complete an electrical circuit with the first electrode when
delivering a therapeutic electrical stimulus. Alternatively, the
housing can be provided with a separate second electrode, carried
thereon, to complete an electrical circuit with the first electrode
when delivering a therapeutic electrical stimulus.
In accordance with the invention, the first electrode can be
adapted and configured to slideably engage the stem element, a
biasing element being provided between the electrode and stem
element for urging the first electrode toward the brain of the
patient. The stem element can be provided with a groove for
engaging the biasing element, to prevent unintentional relative
translation between the stem element and the biasing element.
In accordance with the invention, an aperture can be defined in the
housing, configured and adapted to receive passage of an antenna,
extending from the stimulus generating means outside of the
housing. Further, a feedthrough element can be provided within the
aperture to seal an internal environment of the housing from the
external environment of the housing. Alternatively or additionally,
an aperture can be defined in the housing, configured and adapted
to receive passage of a conductor, extending from the stimulus
generating means to the first electrode.
In accordance with another aspect of the invention, a system for
therapeutic neurostimulation is provided that includes a plurality
of implantable neurostimulators as set forth herein and/or separate
electrodes, and communication means connecting the plurality of
neurostimulators and/or electrodes. The plurality of implantable
neurostimulators and/or electrodes can be arranged in an array in
the cranium of the patient. The array can be a rectangular or
circular array, for example. The plurality of implantable
neurostimulators and/or electrodes can be adapted and configured to
communicate with one another by way of a conductive element, such
as a conductive lead provided between implantable neurostimulators
and/or electrodes. Alternatively or additionally, the
neurostimulators can be adapted and configured to communicate with
one another by way of a wireless signal, such as but not limited to
bluetooth, Wi-Fi or other RF signal. In accordance with this aspect
of the invention, at least one implantable neurostimulator and/or
electrode can be adapted and configured to receive power from at
least one other implantable neurostimulator by way of a conductive
element, such as a lead, provided between implantable
neurostimulators. In accordance with this aspect or other aspects
of the invention, a programmer can be provided external to the
patient for programming a predetermined treatment protocol into at
least one implantable neurostimulator.
In accordance with another aspect of the invention, a method for
using motor evoked potential (MEP) for determination of optimal
treatment parameters is provided. The method can include the steps
of a) implanting a primary stimulating electrode in a target region
of the brain cortex, in which treatment is desired; b) implanting a
satellite stimulating electrode arranged on the motor cortex of the
patient's brain; c) stimulating the motor cortex a first time by
way of the satellite stimulating electrode and measuring a motor
evoked potential (MEP) at a muscle corresponding to the stimulated
region of the motor cortex; d) stimulating the target region of the
brain by way of the primary stimulating electrode; e) stimulating
the motor cortex a second time by way of the satellite stimulating
electrode and measurement of motor evoked potential (MEP) at the
muscle corresponding to the stimulated region of the motor cortex;
f) comparing the cortical excitability between the first motor
cortex stimulation and the second motor cortex stimulation; g)
determining optimal treatment parameters based on the compared
cortical excitability; and h) stimulating the target region by way
of the primary stimulating electrode for a treatment duration.
The method can further include repeating of steps c through g
during or after a prescribed course of treatment.
In accordance with the invention, AC (alternating current) or DC
(direct current) can be used. For instance, in cases such as
epilepsy or Parkinson's disease, in which brain excitability
increases, high frequency AC stimulation or cathodal DC stimulation
is effective in reducing the excitability. On the other hand, as in
cases of stroke, where brain excitability decreases, facilitatory
AC stimulation or anodal DC stimulation is effective. DC
stimulation advantageously permits for effective and safe low
current stimulation.
BRIEF DESCRIPTION OF THE DRAWINGS
So that those having ordinary skill in the art to which the subject
invention pertains will more readily understand how to make and use
the stimulation system of the subject invention without undue
experimentation, embodiments thereof will be described in detail
below with respect to the figures, wherein:
FIGS. 1a-f illustrate a neurostimulator constructed in accordance
with one embodiment of the subject invention, wherein the main body
of the neurostimulator directly engages the cranium of a
patient;
FIGS. 2a-f illustrate a neurostimulator constructed in accordance
with another embodiment of the invention, wherein the main body of
the neurostimulator directly engages the cranium of a patient by
way of a threaded interface;
FIGS. 3a-f illustrate another embodiment of a neurostimulator
constructed in accordance with the invention, wherein the main body
of the neurostimulator engages the cranium of a patient by way of
an intermediate mounting bracket into which the neurostimulator is
snap-fitted;
FIGS. 4a-d illustrate a further embodiment of a neurostimulator
constructed in accordance with the invention, wherein the main body
of the neurostimulator engages the cranium of a patient by way of
an intermediate mounting bracket with which the neurostimulator is
threadedly engaged;
FIGS. 5a-d illustrate a neurostimulator constructed in accordance
with yet another embodiment of the invention, where the
neurostimulator main body is attached to the cranium by way of a
strap-type mounting bracket;
FIGS. 6a-e illustrate a further embodiment of a neurostimulator
constructed in accordance with the invention, which mounts to the
cranium by way of tabs that project from the housing;
FIGS. 7a-e illustrate a further embodiment of a neurostimulator
constructed in accordance with the invention, wherein the main body
of the neurostimulator engages the cranium of a patient by way of
an intermediate mounting bracket with which the neurostimulator is
threadedly engaged;
FIGS. 8a-e illustrate yet another embodiment of a neurostimulator
constructed in accordance with the invention, wherein the main body
of the neurostimulator engages the cranium of a patient by way of
an intermediate mounting bracket with which the neurostimulator is
threadedly engaged, and wherein spacing shims are arranged between
the mounting bracket and the neurostimulator main body;
FIGS. 9a-c illustrate embodiments of networked neurostimulator
systems arranged in respective arrays in accordance with the
invention (One or more electrodes can be used in combination with
or in place of one or more secondary neurostimulators in this or
other embodiments set forth herein);
FIG. 10 illustrates networked neurostimulator(s) and/or electrodes
in accordance with the invention, wherein intradural-type and
extradural-type electrodes are used jointly in the same
network;
FIG. 11a illustrates networked neurostimulators in accordance with
the invention, wherein satellite neurostimulators and/or electrodes
are physically arranged in parallel to a controlling
neurostimulator;
FIG. 11b illustrates networked neurostimulators in accordance with
the invention, wherein satellite neurostimulators and/or electrodes
are physically arranged in series to a controlling
neurostimulator;
FIG. 11c illustrates networked neurostimulators in accordance with
the invention, wherein a satellite neurostimulator and/or electrode
and a controlling neurostimulator are mutually connected and are
arranged on the patient's brain to effect the premotor cortex and
Broca's area;
FIG. 11d illustrates networked neurostimulators in accordance with
the invention, wherein a satellite neurostimulator and/or electrode
and a controlling neurostimulator are mutually connected and are
arranged on the patient's brain for stimulation of the premotor
area on one side and motor cortex on the other side;
FIG. 12a illustrates networked neurostimulators and/or electrodes,
which may include separate electrodes, in accordance with the
invention, arranged on a patient's brain, and prepared for use in
calibrating a treatment protocol by measuring brain excitability by
way of induced motor evoked potential;
FIG. 12b illustrates networked neurostimulators in accordance with
the invention, wherein a remotely situated control unit, which can
include a pulse generator and additionally can include electrodes,
is connected to a plurality of additional electrodes for evoking a
motor evoked potential (MEP) and for providing therapeutic
electrical field, respectively;
FIG. 12c illustrates networked neurostimulators in accordance with
the invention, wherein a controlling neurostimulator is connected
to a plurality of electrodes, which can be controlled by two or
more independent control channels;
FIG. 12d illustrates another embodiment of networked
neurostimulators in accordance with the invention, wherein a
controlling neurostimulator is connected to a plurality of
electrodes, which can also be controlled by two or more independent
control channels;
FIGS. 13a and 13b illustrate further embodiments of networked
neurostimulators in accordance with the invention, wherein a
controlling neurostimulator is connected to a plurality of
electrodes or neurostimulators, which can be controlled by two or
more independent control channels; and
FIGS. 14a and 14b illustrate relatively long electrodes, in depth,
in accordance with the invention that are particularly advantageous
for stimulating regions deeper within the brain than the cerebral
cortex.
DETAILED DESCRIPTION
Referring now to the figures, FIGS. 1a-f illustrate a
neurostimulator constructed in accordance with one embodiment of
the subject invention, designated generally by reference number
100. FIG. 1a is a partial cutaway view of the neurostimulator 100
implanted in the cranium 187 of a patient. Also illustrated in
these figures are the patient's brain 185, dura 181 of the brain,
and cerebrospinal fluid 183 (FIG. 1f) residing therebetween.
The neurostimulator 100 includes a housing 110, and a stem 120
arranged between the housing 110 and an electrode 140 or "brain
electrode". A resilient element, in this case a spring 130, is
arranged between the stem 120 and the brain electrode 140. The
spring biases the brain electrode 140 against the dura 181 of the
brain of a patient during use, ensuring contact with the dura, but
allowing the brain to move as necessary. Accordingly, a low spring
constant may be used, so as to minimize resistance to movement of
the brain. The length of the stem 120, by virtue of its
positioning, sets a minimum distance between the housing 110 and
the brain electrode 140. That is, when the spring 130 is fully
compressed, a minimum distance is still maintained between the
housing 110 and the brain electrode 140. An annular groove 123 is
optionally provided in the distal end of the stem 120 to engage the
spring 130, and prevent unintentional lateral movement of the
spring, particularly when the spring 130 is compressed.
A proximal barb end 141 of the electrode 140 is received through a
central aperture 127 provided in the distal end of the stem 120. It
is typically preferred that either the stem 120, a portion thereof,
or the barb end 141 be constructed of a material capable of
elastically deforming sufficiently so as to allow entry of the barb
end 141 through the aperture 127, but sufficiently stiff so that
pull out of the barb end 141 from the aperture 127 is inhibited. As
best seen in FIG. 1f, the barb end 141 then engages an inner distal
wall 129 of the stem 120, inhibiting withdrawal therefrom. The
spring 130 is thus held between the stem 120 and the brain
electrode 140, and biases the electrode 140 distally with respect
to the housing 110.
Neurostimulators in accordance with the invention are also provided
with mounting capability for securing the neurostimulators to the
cranium 187 of a patient. In the embodiment of FIGS. 1a-f, and as
best seen in FIG. 1e, the neurostimulator 100 includes a close fit
between the cranium 187 and stem 120. The cranium 187 and stem 120
mutually engage along the wall of the aperture 189. The engagement,
in accordance with this aspect of the invention can be a
compression fit, provided by a tapered aperture and matching stem
shape, a friction fit due to a surface texture of the brain stem
120, a surface texture that promotes bone ingrowth, or any
combination thereof.
Also, the housing 110, encloses the necessary components for
effecting a therapeutic neurostimulation. Depending on the precise
implementation, components housed within the housing 110 can
include a receiver, a processor, memory, power storage components
and/or a pulse generator, for example. The internal components can
be attached to an internal or external antenna, such as external
antenna 115. If provided with an external antenna, such antenna can
pass through an insulated feedthrough (described in more detail in
connection with the embodiment of FIGS. 6a-e).
The internal componentry is also electrically connected to the
electrode through a conductive element or lead, which can be, for
example, a wire 116, as shown in FIG. 1f. As with an external
antenna, the wire 116 passes through an insulated feedthrough (also
described in connection with the embodiment of FIGS. 6a-e) when
passing through the housing 110. The internal componentry can, once
set, control the treatment parameters, including mode (AC or DC),
duration, polarity (anodal or cathodal), frequency and intensity of
stimulation, for example, unipolar stimulation with 1 volt, at 50
Hz and a pulse width of 190 seconds.
The housing 110 may itself act as a second or "ground" electrode,
completing a circuit with the first electrode 140, which contacts
the dura 181 of the patient's brain 185. Accordingly, in such
instances, it is particularly important in such embodiments for the
conduction path from internal components to the brain electrode 140
to be insulated from the housing. In alternate embodiments, the
housing 110, or parts thereof can be configured to be insulating
and only have predetermined regions that function as second
electrodes. Alternatively still, secondary electrodes can be
carried by the housing 110, and may be arranged at any appropriate
location thereon, such as at the proximal end of the
neurostimulator 100, opposite the distal end, which has the brain
electrode 140 arranged thereon.
The brain electrode can have any shape desired, but in the
illustrated embodiments has a generally circular shape. The distal
end surface of the brain electrode 140, which contacts the dura 181
is conductive in order to deliver a therapeutic electric field to
effect neurostimulation in the targeted region. Optionally, the
brain electrode 140, can include a plurality of discrete
stimulation regions defined thereon. Such stimulation regions can
be mutually divided by, for example, insulating regions disposed
therebetween. Alternatively, the stimulation regions can be
conductive elements disposed on an otherwise nonconductive brain
electrode body. It is envisioned and well within the scope of the
subject disclosure that the electrode 140 can be configured for
unipolar or multipolar operation, including bipolar, quadripolar or
octopolar operation, depending on the stimulation characteristic
that is desired. In a unipolar or monopolar application, the
housing 110 can serve as the ground or anode contact. Those skilled
in the art will readily appreciate that the shape and/or
configuration of the electrode 140 can vary depending upon the
stimulation characteristic that is desired. For example, without
limitation, the electrode 140 can be circular, annular or
polygonal. It is envisioned that the electrode 140 can be
configured as a paddle having one or more surface electrodes
mounted thereon. Multiple electrodes can be aligned or otherwise
arranged on the paddle in a manner to achieve a certain electrical
field distribution pattern. It is also envisioned that two or more
networked stimulators can be implanted, so that both work in
conjunction to achieve a desired stimulation effect, which will be
described in more detail below.
Therefore, power stored in the internal componentry within the
housing 110 can be supplied through a conductive element, such as a
conductive lead 116 to the brain electrode 140 and into the brain
185 of the patient. The circuit is completed through the
surrounding tissue in a more diffuse manner than in the immediate
area of the brain electrode 140, completing the circuit to the
second electrode, which can be the housing 110 itself, depending on
the precise implementation. As set forth above, particularly when
provided with a resilient member, such as a spring 130, the brain
electrode 140 maintains contact with the dura 181 of the brain 185,
even if the brain should move slightly.
As best seen in FIG. 1d, a programmer 190 with transceiver 195 can
be placed in proximity to the neurostimulator 100, to enable
one-way or two-way communication with the neurostimulator. The
programmer 190 can be used to initiate and control treatment, or
simply to program the neurostimulator 100 for autonomous operation
with the desired treatment protocol, including variable parameters
such as AC or DC stimulation, duration, pulse width, amplitude,
timing of treatment, frequency and polarity. Data transmitted to
the neurostimulator relating to such treatment protocol is stored
by the neurostimulator in memory provided in the circuitry within
the housing 110, and is utilized to control operation of the
neurostimulator 100 through a processor or similar element. If
desired, the neurostimulator can be used to monitor neural activity
in the brain of the patient, as an alternative or in addition to
stimulation of the brain. Information regarding such neural
activity can be stored within memory of the neurostimulator and
later communicated to the programmer 190, or can be immediately
transmitted to the programmer 190.
Additionally, if so desired, the programmer 190 and neurostimulator
can be configured and adapted such that the programmer 190 is
capable of recharging the neurostimulator 100, such as by inductive
transfer of power to a charging circuit within the neurostimulator.
In such an embodiment, the programmer transceiver 195 and
neurostimulator 100 are each provided with a coil, the coil in the
programmer inducing a current in the coil of the neurostimulator
100 to recharge one or more batteries in the neurostimulator
100.
The neurostimulator 100 is formed out of biocompatible materials
such as a biocompatible polymeric material, titanium alloys, alloys
of other metals and/or ceramic materials, for example. While many
biocompatible materials are suitable based on biocompatibility and
strength, it is also important that the materials used do not
affect and are not affected by ordinary environmental factors,
including exposure to magnetic fields that might be encountered in
an MRI device, or x-rays that may also be used in medical imaging,
for example. In a preferred embodiment, the housing 110 is formed
of titanium alloy, the stem 120 is formed of a nonconductive
polymeric material, and the spring 130 and brain electrode 140 are
formed of titanium alloy. A conductive lead 116 is also preferably
formed of titanium alloy, but can be of another conductive
material.
Components that must be mutually attached, such as components
forming the housing 110, can be attached with any suitable method,
such as adhesives including epoxies, welding and the like. In a
preferred embodiment, attached components are laser welded to one
another.
If bone ingrowth into a component of the neurostimulator 100 is
desired to help anchor the neurostimulator in place, such as into
the stem 120, the stem 120 can be formed of a porous ceramic
material, a sintered metal material and/or a material having a
hydroxyl apatite coating, for example. Also, although shown with a
square incision in FIG. 1b, for example, it is to be understood
that differently shaped incisions are applicable, including linear
incisions.
Neurostimulators in accordance with the invention can be any size
necessary, although in general are not very large. In accordance
with one embodiment of the invention, the housing 110 is about 25
mm in diameter, while the stem 120 is about 10.5 mm in diameter,
with the overall height of the neurostimulator being about 18.5
mm.
FIGS. 2a-f illustrate a further embodiment of a neurostimulator 200
constructed in accordance with the invention. The neurostimulator
is similar in many respects to the neurostimulator 100 of FIGS.
1a-f, and therefore, like reference numbers have been used to refer
to like elements. The neurostimulator 200 of FIGS. 2a-f differs
from the embodiment of FIGS. 1a-f primarily in the connection
between the neurostimulator 200 and the cranium 187 of the patient.
The neurostimulator 200 includes a stem 220 having threads 225
formed on the outer surface thereof. As best seen in FIGS. 2d-f,
the threads 225 engage the cranium 187, inhibiting direct pullout
of the neurostimulator 200. The threads 225 can be adapted and
configured to "self-tap" the cranium 187, or can be inserted into
the cranium 187 following a tapping step, whereby a helical groove
is cut into the edge of the aperture 189 formed in the cranium
187.
Insertion of the neurostimulator 200 into the aperture 189 is
effected by way of screwing the neurostimulator into the aperture
189. As the neurostimulator 200 advances through the aperture, the
brain electrode 140 will eventually come into contact with the dura
181. Advancement may be stopped any point desired, or the
neurostimulator 200 can be advanced fully into the aperture 189 to
a point where the housing 110 abuts the upper surface of the
cranium 187, for example.
The stem 220 includes at its distal end, a recess 224 in which the
resilient member--again, a spring 130--partially resides. This
recess 224 serves the purpose of the annular groove 123 of the
neurostimulator 100 of FIGS. 1a-f by stabilizing the spring 130,
preventing the spring from dislodging from the stem 220. Naturally,
a groove, such as groove 123 can be applied to this embodiment as
well. The brain electrode 140 is inserted through the aperture 227
formed in the stem 220, with its barb end 141 engaging the distal
internal wall 229 of the stem 220 and compressing the spring
130.
FIGS. 3a-f illustrate various views of another embodiment of a
neurostimulator 300 constructed in accordance with the invention.
Where the foregoing embodiments are configured to directly engage a
wall of an aperture 189 formed in the cranium 187 of a patient, the
neurostimulator 300 of FIGS. 3a-f is provided with a mount 350,
which is first inserted into the aperture 189, before the remainder
of the neurostimulator 300. The mount 350, as embodied, includes an
annular body 355 and an attached flange 353 with screw holes 352
formed therein. Screws 351 are used to attach the mount 350 to the
cranium 187.
The main body portion 301 of the neurostimulator 300, which
includes the housing 110, stem 320, spring 130 and electrode 140,
are then inserted into the mount 350. In the embodiment illustrated
in FIGS. 3a-f, and as best seen in FIGS. 3b, 3c and 3e, annular
barbs 325 are arranged on the outer surface of the stem 320, and
engage mating annular recesses 357 in the mount 350. The distal
face of each annular barb 325 is angled, and the proximal face is
perpendicular with respect to the longitudinal axis of the
neurostimulator 300 in order to facilitate insertion into while
inhibiting removal of the main body portion 301 from the mount
350.
Although illustrated in FIGS. 3a-f with equal numbers of annular
barbs 325 and annular recesses 357, specifically, two of each, this
need not be the case. The neurostimulator 300 can be configured so
that the increments between annular barbs and recesses, or similar
mutually engaging elements provides a range of insertion increments
which can allow the surgeon to advance the main body portion 301 of
the neurostimulator 300 in the mount 350 incrementally until the
desired contact, as gauged by pressure or electrical conductivity
with the brain, for example, is reached. Such increments can be
relatively large, as illustrated, or can be much smaller, such as
at 0.5 mm increments, for example.
Naturally, the precise configuration of the engagement need not be
as illustrated. Other configurations that enable a snap-fit of the
main body portion 301 into the mount can be applied to the present
embodiment or other embodiments set forth herein. An alternate
attachment to a mount is illustrated in the embodiment of FIGS.
4a-d. Alternatively, other types of mutual engagement are
applicable to this aspect of the present invention, including a
bayonet-type locking feature, for example.
Moreover, the mount 350 is illustrated with a flange 353 that
mounts to the outer surface of the cranium 187, which results in
the housing 100 extending a small distance about the surface of the
cranium 187. Although the distance that the housing 100 extends
above the cranium 187 is not large, the mount 350 can be adapted so
that the housing 110 is partially or fully recessed below the outer
surface of the cranium 187. Naturally, the diameter of the housing
100 can be relatively smaller, so that the entire main body portion
301 can fit within the mount 350. These optional features may also
advantageously be applied to other embodiments of neuro stimulators
described herein.
FIGS. 4a-d illustrate a further embodiment of a neurostimulator 400
in accordance with the invention. Elements that are identical to
foregoing embodiments are indicated by the same reference number,
and analogous elements are indicated by similar reference numbers.
As with the embodiment of FIGS. 3a-f, the neurostimulator includes
a mount 450 into which a main body portion 401 is inserted. In this
embodiment, the stem 420 includes helical threads on the outer
surface thereof to engage a matching helical groove 457 in the
mount 450. The mount 450 includes a mounting flange as with the
embodiment of FIGS. 3a-f, which is first attached to the cranium
187. Of course, if desired, the main body portion 401 of the
neurostimulator can be attached to the mount 450, and then attached
to the cranium by screws 351. As with any embodiment set forth
herein, the stem 420 can be provided with a groove 123 as
illustrated in FIG. 1c for retaining the spring 130, or can be
provided simply with a recess 224, as in FIG. 2c.
Advantageously, the nature of the interface between the main body
portion 401, having helical threads 425 on the stem 420 thereof,
and the mount 450, having a mating helical groove 457, allows the
surgeon to adjust the relative position between the mount 450 and
the main body portion 401, and thus also between the brain and the
electrode 140. Such adjustment may be desirable during installation
of the neurostimulator, in order to ensure proper contact between
the electrode 140 and the patient's brain, for example.
With respect to other aspects of the neurostimulator, including the
housing 110, components held therein, the spring 130 and electrode
140, for example, such features can be as described in connection
with other embodiments set forth herein. In general, any feature
described in connection with one embodiment of the invention can be
applied to another embodiment of the invention.
FIGS. 5a-d illustrate various embodiments of neurostimulators
constructed in accordance with the invention, which are secured to
the cranium 187 of the patient by way of a bracket secured over the
neurostimulator 500, and to the cranium 187. In the embodiment of
FIGS. 5a-d, the neurostimulator 500 itself is essentially the same
as, and includes the same basic set of components as the
neurostimulator 100 of FIGS. 1a-f. The neurostimulator 500 can
include any of the attachment features described in connection with
the neurostimulator 100 of FIGS. 1a-f, or can be configured to
simply fit within the aperture 189 formed in the cranium 187 of the
patient without any direct attachment between the neurostimulator
500 and the cranium 187. Instead, a bracket is provided which
engages the neurostimulator 500, and which is directly secured to
the patient's cranium 187, thereby securing the neurostimulator 500
to the cranium 187.
In the embodiment of FIGS. 5a-b, the bracket 560a is substantially
linear in plan view, and includes symmetrical bends, which form a
crook that engages the housing 110. Screw holes are provided in the
ends of the bracket 560a, to allow passage of screws 351 through
the bracket 560a, and into the cranium 187, thereby securing the
bracket 560a and the neurostimulator to the cranium 187.
The embodiment of FIG. 5c illustrates the neurostimulator 500,
which itself is the same as that illustrated in FIGS. 5a-b, and a
generally X-shaped bracket 560b for securing the neurostimulator
500 to the cranium 187 of the patient. As embodied, the bracket
560b is contoured so as to engage the housing 110 when placed over
the housing. Mechanical attachment means for attaching the bracket
560b to the cranium 187 of the patient are provided--particularly,
screw holes placed at the ends of the bracket for use with screws
351. Further, if desired, a seal 581 can be provided between the
cranium 187 and the neurostimulator 500 to compensate for any
irregularities therebetween. The seal 581 can be applied directly
to the cranium 187, directly to the neurostimulator 500, or can be
in the form of an O-ring, for example, that is placed between the
cranium 187 and the neurostimulator 500. Naturally, this feature
can be applied to any embodiment set forth herein.
The embodiment of FIG. 5d illustrates still another embodiment of
the neurostimulator and a securing bracket 560c. In this
embodiment, the bracket 560c includes an enlarged cap portion 567
and two diametrically opposed tab portions 569, for securing the
cap 560c and the neurostimulator 500 to the cranium of the patient
187, by way of screws, for example. The cap 560c can be provided
with a circumferential lip 565, as illustrated, to aid engagement
with the neurostimulator 500.
FIGS. 6a-6e illustrate a further embodiment of a neurostimulator
600 in accordance with the invention. As seen in FIGS. 6a and 6b,
the neurostimulator 600 is attached to the cranium 187 with screws
351, which are inserted through radial tabs 617 extending from the
housing 610 of the neurostimulator 600.
FIGS. 6c-6d are exploded views of the neurostimulator 600,
illustrating individual components thereof and their relative
orientation with respect to one another. The housing 610 includes
both a cap portion 610a and a floor portion 610b. The cap portion
610a is arranged at the proximalmost end of the neurostimulator 600
and includes an aperture 613, which permits an insulated
pass-through 614 for the antenna 115 to pass through the housing
610, if so-embodied. Alternatively, the antenna may be fully
contained internally to the housing. In either case, the antenna
115 is connected to internal componentry 619 of the neurostimulator
600. A floor portion 610b of the housing 610 is sealed to the cap
portion 610a, securing within the housing 610, the internal
componentry 619. The floor 610b can be sealed with a polymeric
adhesive or sealant, or in a preferred embodiment, laser welded
thereto. A second insulated pass-through 624 is provided in the
floor 610b, which allows a therapeutic electrical impulse to reach
the electrode 140 by way of a conductor 680 connected therebetween,
through the floor 610b.
A retainer ring 611 is secured to the floor 610b, and facilitates
engagement between the housing 610 and the stem 620. The retainer
ring 611 is preferably made of the same material as the housing and
attached thereto by laser welding, or integrally formed therewith.
Alternatively, the retainer ring 611 can be made of any suitable
material of sufficient strength and durability. Moreover, the
retainer ring 611 can be provided with a stepped undercut 612 (FIG.
6d) to facilitate a snap-fit engagement with the proximal end of
the stem 620, where the stem 620 is provided with a mating
engagement feature, such as undercut 622. The retainer ring 611 can
also be formed so as to include a split 616, which can have a
corresponding protrusion 621 arranged on the stem 620. Together,
the split 616 and the protrusion 621 inhibit relative rotation
between the stem 620 and the retainer ring 611.
The stem 620, as set forth above, can be configured to engage with
the housing, particularly the retainer ring 611, by snap fit. Such
snap fit is preferably sufficiently robust enough that no other
mechanical connection between the stem 620 and housing 610 is
required. However, if desired, adhesive can be alternatively or
additionally used to connect the stem 620 and the housing 610.
Naturally, other mechanical connections can be used in place of
that described above without departing from the scope of the
invention. As with the embodiment of FIGS. 1a-f, a groove 623 can
be provided on the distal end of the stem 620 for engaging the
spring 130. The aperture 627 provided in the stem 620 receives the
proximal end of the electrode 140, as described in connection with
the embodiment of FIGS. 1a-f, thereby holding the spring in place
therebetween.
FIGS. 7a-e illustrate a further embodiment of a neurostimulator 700
constructed in accordance with the invention. The neurostimulator
includes a mount 750 into which a main body portion 701 is
inserted. In this embodiment, the stem 720 includes helical threads
721 on the outer surface thereof to engage matching helical threads
751 in the mount 750. The mount 750 includes a mounting flange as
with foregoing embodiments. In use, the mount 750 is first attached
to the cranium 187, with the main body portion 701 being inserted
thereafter. Of course, if desired, the main body portion 701 of the
neurostimulator can be attached to the mount 750, and subsequently
attached to the cranium by screws or other suitable attachment
means. As with any embodiment set forth herein, the stem 720 can be
provided with a groove 123 as illustrated in FIG. 7c for retaining
the spring 130. Alternatively, the stem 720 can simply be provided
with a recess as shown by recess 224, of FIG. 2c. Advantageously,
the threaded interface between the stem 720 and mount 750 allows
for adjustability, if adjustability is desired or required.
The retainer lip 711 provided in the embodiment of FIGS. 7a-7e
includes a discontinuity 716, as best illustrated in FIGS. 7c and
7d. This allows for locking engagement with the stem 720. The
discontinuity 716 in the retainer lip 711 allows, more
specifically, for engagement with locking anti-rotation protrusion
726 provided on the stem 720. The retainer lip 711 and the mutually
engaging part of the stem 720 can be shaped to as to allow for a
press-fit, snap-fit or other secure mutual engagement arrangement.
If so desired, the mutual engagement of the retainer lip 711 and
stem 720 can be permanent or reversible, depending on the precise
implementation.
Additionally illustrated is an electrical a conductor 780, which
leads from the feedthrough 624 provided in the lower wall 618 of
the housing 710, to the electrode 140. Accordingly, a therapeutic
electrical stimulus can be delivered through the electrode to the
patient's brain.
Moreover, as with other embodiments described herein, the housing
710 can include additional components held therein. In general, any
feature described in connection with another embodiment of the
invention can be applied to the embodiment illustrated in FIGS.
7a-7e.
FIGS. 8a-e illustrate a further embodiment of a neurostimulator 800
designed and constructed in accordance with the invention. As with
some or all of the foregoing embodiments, the neurostimulator 800
is provided with a housing 810 having a bottom wall 818, a mount
850 for mounting to the cranium 187, internal componentry 619, a
stem 820, and other elements. What is notably different between the
neurostimulator 800 of FIGS. 8a-8e is the absence of a resilient
biasing member such as a spring. Instead, spacing between the
electrode 140 and brain is determined and maintained by shims 880
which reside between the housing bottom wall 818 and the mount 850.
The housing 810 is connected through its bottom wall 818, retainer
lip 711 to the stem 820. The electrode 140 also engages the stem
820, which in-turn engages the mount 850. Although threads 821 are
illustrated, other engagements are conceived to allow relative
mutual engagement such as a bayonet-type key-and groove of
press-fit, for example. Such mutual engagement, in cooperation with
the shims 880, maintains the relative spacing between the electrode
140 and the patient's brain.
Further in accordance with the invention, neurostimulators are
provided which are adapted and configured to be networked to
operate jointly in order to effect a therapeutic result. Under
normal circumstances, a healthy, uninjured brain utilizes multiple
regions simultaneously to conduct unique function. For example,
speech requires coordination between different areas of the brain,
including Broca's area, Wernicke's area and a supplementary motor
area. Following injury resulting in brain damage, such as stroke,
functional reorganization of the surviving portions of the brain
occurs to compensate for lost function. Regions surrounding those
previously engaged in the same function are conscripted for
reorganization. Such areas are usually larger than the areas that
formerly performed that function Applicant recognizes that
neurostimulation can enhance the recovery process, and if multiple
areas are necessary for recovery, that it is beneficial to
co-stimulate such areas, which can include excitation or
inhibition, depending on the status of that region of the
brain.
Networking of a plurality of discrete neurostimulators, as
described hereinabove, can achieve the aforementioned result. If
actuated simultaneously, such a plurality of neurostimulators can
yield an electrical field of increased size that is capable of
stimulating a larger area than a single, discrete neurostimulator
alone. Such stimulation can enhance cortical plasticity and
therefore can enhance recovery. Through the use of electronic
controls, different electrodes of the neurostimulator(s) can be
activated at different times and with different therapeutic
parameters, including different mode (anodal or cathodal) voltage,
duration and interval between successive impulses.
Alternating current (AC) or direct current (DC) can be used as
required or desired to achieve the desired stimulation. For
instance, in cases such as epilepsy or Parkinson's disease, in
which brain excitability increases, high frequency AC stimulation
or cathodal DC stimulation is effective in reducing the
excitability. On the other hand, as in cases of stroke, where brain
excitability decreases, facilitatory AC stimulation or anodal DC
stimulation is effective. Moreover, individual neurostimulators in
accordance with the invention may be equipped with multiple
electrodes. Such multiple electrodes can be adapted to have the
same polarity and act as in unison as a single pole, with a
relatively remotely oriented opposite pole, such as the housing of
the neurostimulator, as described above. Alternatively, the
multiple electrodes can be adapted to have opposite polarity to one
another in order to effect simulation in the areas immediately
surrounding the electrodes. For example, in stroke patients,
ipsilateral premotor area requires facilitatory stimulation;
whereas the contralateral motor area may require inhibitory
stimulation.
FIGS. 9a-9c illustrate embodiments of neurostimulator systems
arranged in respective arrays 900a, 900b, in accordance with the
invention. The array of FIG. 9a is a rectangular array, while the
array of FIG. 9b is substantially circular in shape. As
illustrated, a controlling neurostimulator 901 is provided in
combination with companion neurostimulators 905, which
alternatively can be embodied simply as electrodes. For simplicity,
such alternatives may not be pointed out in each instance
throughout this document, but it is to be understood that such a
substitution can be made, and in some cases may be preferable. The
controlling neurostimulator 901 and companion neurostimulators 905
are networked so as to synchronize therapeutic treatment across
various regions of the brain.
The networking can be effected wirelessly or with a physical
conductive lead 904. The systems can be configured so that the
conductor 904 carries data, such as may be received from a
programmer 190. Additionally or alternatively, power may be
transmitted through the conductor 904 to drive each companion
neurostimulator 905. The power supplied can go through internal
componentry in the companion neurostimulator 905, or alternatively,
the power can be a therapeutic electrical impulse that is merely
passed through the companion neurostimulator 905 to the patient's
brain. Accordingly, the companion neurostimulators 905 can be
physically configured in the same manner as those neurostimulators
described herein in connection with the foregoing embodiments, or
alternatively, the companion neurostimulators 905 can be simpler in
construction. Naturally, if electrodes lacking the capability to
independently generate a therapeutic impulse are used, another
pulse generator, such as one housed within a controlling
neurostimulator is used, with the power being transmitted by way of
a conductive lead.
Alternatively still, the companion neurostimulators can receive a
control signal from the controlling neurostimulator 901, which
triggers the companion neurostimulator(s) to release a therapeutic
electrical impulse.
Further, the companion neurostimulators 905 can be essentially
autonomous, being addressed only initially or periodically to set
treatment protocol.
FIG. 9c schematically illustrates an arrangement for connection of
the controlling neurostimulator 901 and the companion
neurostimulators 905 by way of the conductor 904. The conductor 904
is preferably well insulated, for example by a sheath of silicone
rubber. The neurostimulators 901, 905 can be adapted to
automatically puncture the sheath when applied thereto. Moreover,
if an error is made in placement, a repair covering 908 can be
applied over the conductor to prevent an errant electrical
discharge.
FIG. 10 is a partial view of an embodiment in accordance with the
present invention including networked neurostimulators, including
an extradural-type neurostimulator 1000b, such as those described
above, used in combination with an intradural-type neurostimulator
1000a. The intradural neurostimulator 1000a is particularly useful
in cases of brain atrophy, where the brain electrode, such as brain
electrode 1040b, would not rest close enough to the brain cortex to
result in an electrical field adequate to evoke a therapeutic
response. The electrode 1040b of the extradural neurostimulator
1000b terminates external with the dura 181. However, if the brain
cortex has atrophied due to a stroke or for other reasons, the
electrode 1040b may not rest near enough to the cortex to be
effected by the electrical field transmitted through the electrode
1040b.
However, the intradural neurostimulator 1000a is adapted and
configured to extend through the dura 181 of the brain 185, and
therefore terminates more closely to the brain cortex in atrophied
regions. The electrode 1040a of the intradural neurostimulator
1000a can be adapted and configured to include a relatively
spheroidal shape, as illustrated in order to better distribute a
therapeutic electrical field to the surrounding neural tissue, and
to prevent damage to the surrounding cortical surface.
As with foregoing embodiments, a conductor in the form of a
conductive lead 1004 can be used to interconnect all
neurostimulators, electrodes, and/or separate implantable control
units or pulse generators, if so-embodied (see FIG. 12a, for
example). Electrical connections between the neurostimulator(s)
and/or electrode(s) and any conductor(s) can include a through
connection, in which the conductor 1004 continues from one
neurostimulator or electrode to the next, and electrically contacts
a conductive component within the neurostimulator or electrode in
order to transmit a control signal and/or to provide power to the
neurostimulator or electrode. The electrical connection may include
a piercing element that pierces the insulation of the conductor
1004. Such piercing elements can be activated by advancing a screw
or by closing the housing of the neurostimulator over the conductor
1004, for example. However, other connection arrangements can be
utilized in accordance with the invention. Alternatively or
additionally, communication between neurostimulators and/or a
controller can be effected wirelessly, as described
hereinabove.
FIG. 11a illustrates networked neurostimulators and/or electrodes
physically connected in parallel and arranged with respect to the
brain, for premotor, motor cortex, and supplementary motor area
stimulation, as an example. Such arrangements can be embodied such
that all neurostimulators or electrodes are controlled
simultaneously on one control channel, or alternatively, so that
the neurostimulators or electrodes are controlled in one or more
groups, on one or more respective control channels. Accordingly,
the controlling neurostimulator 1100 and the companion
neurostimulators 1105, can be actuated independently with
individual treatment protocol. As illustrated, a controlling
neurostimulator 1100 is connected to three companion
neurostimulators 1105 and/or to simple electrodes. Such companion
neurostimulators can receive power, control signals, or both power
and control signals from the controlling neurostimulator 1100.
Again, if electrodes lacking the capability to independently
generate a therapeutic impulse are used, another pulse generator,
such as one housed within the controlling neurostimulator 1100 is
used, with the power being transmitted by way of a conductive
lead.
Typically, it is necessary that the controlling neurostimulator
1100 be somewhat larger than the companion neurostimulators 1105,
in order to house the necessary power supply and/or electronic
components. Advantageously, companion neurostimulators can be low
profile for cosmetic or other purposes. That is, the housing of the
companion neurostimulators do not necessarily include circuitry of
the controlling stimulator, and can therefore be significantly
smaller than that of the controlling neurostimulator. Thus, a
patient with multiple neurostimulators need not have multiple
noticeable bumps under his or her scalp, although typically, even
the controlling neurostimulators are relatively low-profile in
accordance with the invention.
Accordingly, companion neurostimulators can be similar in
configuration and attachment as those set forth above, for example
in connection with FIGS. 1-8. However, as set forth above,
conventional electrodes can also be used in place of such companion
neurostimulators. Alternatively, any or all of the networked
neurostimulators can have different physical designs, not
specifically set forth herein, but which function in accordance
with the invention.
The embodiment of FIG. 11a, as illustrated, includes representative
electric field lines 1188, representing field lines due to
independent, non-simultaneous activation of the controlling
neurostimulator 1100 and companion neurostimulators 1105 and/or
electrodes. This arrangement is useful for stimulation (activation
or inhibition) of multiple functional regions at different times.
Such stimulation can be contrasted with the effect of simultaneous
stimulation, which is represented in the embodiment of FIG.
11b.
FIG. 11b illustrates networked neurostimulators 1100, 1105
connected in series and also arranged, for example, for premotor
stimulation. The controlling neurostimulator 1100 is connected via
a conductor lead 1104 to companion neurostimulators 1105. As
described above, the connection can be such that it provides power
and/or a controlling signal from the controlling neurostimulator to
the companion neurostimulator(s). The representative electrical
field lines 1188 in FIG. 11b represent a superposition of the
individual electric fields generated by each neurostimulator when
simultaneously activated. Such an arrangement can be useful when it
is desirable to stimulate a large area of the brain
simultaneously.
It should be noted that although the companion neurostimulators
1105 are physically connected in series to the controlling
neurostimulator 1100, they can be configured and adapted to
function independently or jointly in accordance with a prescribed
protocol, for example by receiving and responding only to signals
intended only for that particular companion neurostimulator by way
of a purpose-built electronic circuit, for example. Moreover, the
conducting lead can have a plurality of mutually isolated
conductors therein, for delivering signals to selected companion
neurostimulators.
FIG. 11c illustrates a controlling neurostimulator 1100 and
companion neurostimulator 1105 arranged for stimulation of the
premotor cortex and Broca's area, for example. This arrangement is
advantageous, because patients with strokes in the dominant
hemisphere can simultaneously have motor weakness and language
impairment. As with the foregoing embodiments, the neurostimulators
can be connected by way of a conductive lead 1104. As illustrated,
example electric field lines 1188 are provided to illustrate the
extent of stimulation when the controlling stimulator 1100 and
companion neurostimulator 1105 release a therapeutic electrical
impulse simultaneously.
FIG. 11d illustrates a controlling neurostimulator 1100 and
companion neurostimulator 1105 arranged for bilateral or
"contralateral" premotor stimulation, for example. A treatment
protocol where corresponding regions are treated simultaneously can
enhance recovery. Motor recovery may be hampered by the increase of
inhibitory influence of the contralateral hemisphere. Therefore,
this inhibitory influence may be required (disinhibition) to be
inhibited for the recovery of ipsilateral motor weakness from
stroke.
Advantageously, the systems of FIGS. 12a-12c can be used for
treatment to enhance recovery following brain injury. As
illustrated in FIG. 12a, the systems of FIGS. 12b-12d, as well as
other embodiments set forth herein, can be configured and adapted
to calibrate a treatment regimen by measuring brain excitability
prior to treatment. As illustrated, the satellite electrode is
arranged on the motor cortex, while the other stimulating
electrode(s) is (are) arranged elsewhere on the brain. To measure
brain excitability, the satellite electrode 1205 releases an
electric impulse, which then evokes a motor response, which is
measured by electrode 1287, arranged on the patient's hand, for
example at the first digital interosseous muscle, which procedure
is carried out before delivering the main stimulation. Following
stimulation for determined periods of time, the motor evoked
potential (MEP) can then be measured again. Comparison of MEP
before and after the stimulation can provide a gauge to the
physician as to how much stimulation by the electrode(s) 1203a will
be necessary to achieve the desired results. Naturally, the
satellite electrode 1205 may include a shape and attachment means
to the cranium, as described hereinabove in connection with
neurostimulators.
FIG. 12b illustrates a networked neurostimulation system in
accordance with the invention, which has not been implanted. The
system includes a surgically-implantable remote power and pulse
generator or control unit 1209, a stimulating electrode array
1203a, including a plurality of contacts, and a satellite electrode
1205. The stimulating electrode array can be replaced by one or
more neurostimulators having a configuration set forth herein, if
desired, and as will be seen in connection with following
embodiments. The satellite electrode is usually placed on the motor
cortex and delivers electrical impulse to evoke a motor response in
the corresponding extremity. The companion neurostimulator can be
of a conventional design or can be constructed in accordance with
any of the foregoing embodiments, for example, but in which the
necessary circuitry and power source is provided in the separate
control unit 1209. In such an embodiment, the control unit 1209 is
preferably surgically implanted in the same location, as would be a
conventional pacemaker.
FIG. 12c illustrates a further embodiment of a networked
neurostimulation system in accordance with the invention. In this
embodiment, the controlling neurostimulator 1200 includes the
necessary power supply and componentry to control the companion
neurostimulators 1203b and the satellite electrode 1205.
Preferably, these two sets of components branching off of the
controlling neurostimulator 1200, are connected to two separate
channels of the controlling neurostimulator 1200 for independent
operation.
FIG. 12d illustrates an embodiment of yet another system in
accordance with the invention that essentially combines features of
the embodiments of FIG. 12b and FIG. 12c. A controlling
neurostimulator 1200 is provided in conjunction with an array
1203a, and a satellite electrode 1205, which can be, more
particularly, a neurostimulator as set forth above, or of another
design.
FIGS. 13a and 13b illustrate example arrangements for inhibiting
temporal lobe epilepsy (FIG. 13a) and frontal lobe epilepsy (FIG.
13b), respectively. A controlling neurostimulator 1200 is used to
control companion neurostimulators 1203b and the satellite
electrodes 1205. Similarly, a sensor, such as sensor 1287,
connected to relevant analytical equipment can be used to calibrate
treatment protocol for a patient, as illustrated in FIG. 12a.
The invention also, therefore, includes a method for using motor
evoked potential (MEP) for determination of optimal treatment
parameters. In accordance with one embodiment, the invention
includes the steps of: 1.) Implanting a primary stimulating
electrode in a target region of the brain cortex, in which
treatment is desired. Such primary stimulating electrode can be any
of the aforementioned neurostimulators, for example. 2.) Implanting
a satellite stimulating electrode arranged on the motor cortex of
the patient's brain. Such satellite stimulating electrode,
similarly, can be of a construction set forth herein. 3.)
Stimulating the motor cortex a first time by way of the satellite
stimulating electrode and measuring a motor evoked potential (MEP)
at a muscle corresponding to the stimulated region of the motor
cortex. Such muscle can be, for example, the first digital
interosseous muscle. 4.) Stimulating the target region of the brain
by way of the primary stimulating electrode. 5.) Stimulating the
motor cortex a second time by way of the satellite stimulating
electrode and measurement of motor evoked potential (MEP) at the
muscle corresponding to the stimulated region of the motor cortex.
6.) Comparing the cortical excitability between the first motor
cortex stimulation (before target region stimulation) and the
second motor cortex stimulation (after target region stimulation).
7.) Determining optimal treatment parameters based on the compared
cortical excitability. 8.) Stimulating the target region by way of
the primary stimulating electrode for a treatment duration. The
treatment may be prolonged or applied cyclically, depending on the
determined optimal treatment parameters.
If desired, the steps 3 through 7 can be repeated at intervals
during treatment, and/or following treatment to evaluate
improvement and/or to modify treatment parameters.
In accordance with still a further aspect of the present invention,
neurostimulators for implantation within and treatment of deeper
regions of the brain are provided. FIGS. 14a and 14b illustrate
neurostimulators 1400a, 1400b, respectively for extending into the
brain for more direct treatment of deeper lying neural tissue than
possible by superficial cortical stimulation. A disorder requiring
treatment with such a device may be, for example, medial temporal
lobe epilepsy.
As illustrated, each neurostimulator 1400a, 1400b includes a
housing 1410a, 1410b adapted and configured to enclose the
necessary componentry for operation, as described in connection
with other embodiments of neurostimulators hereinabove. Either
neurostimulator can be provided with anchoring capability, such as
a strap 1460. Moreover, each neurostimulator includes a body
portion 1420, on which electrodes 1440 are placed along its length,
which is, in one embodiment about 45 mm. The electrodes 1440 may be
unipolar or bi-polar. That is, they may have the same polarity,
with an opposite pole being located remotely or at the housing
1410a, 1410b of the neurostimulator 1400a, 1400b. Alternatively,
they may include electrodes 1440 of different polarities, such as
polarities that alternate along the length of the body 1420.
While the apparatus and methods of subject invention have been
shown and described with reference to preferred embodiments, those
skilled in the art will readily appreciate that changes and/or
modifications may be made thereto without departing from the spirit
and scope of the subject disclosure. For example, it should be
understood that features described in connection with one
embodiment may equally be applied to other embodiments, even though
not directly described in connection with such other
embodiments.
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